Metal-oxide-semiconductor (MOS) capacitors with polysilicon (Poly-Si) gates have been used to make efficient Electro-optical (EO) modulators on silicon. Such modulators may utilize the refractive index of the silicon occurring via the free carrier plasma dispersion effect to accomplish modulation. For example, through doping, a free carrier density change may cause optical phase modulation on the light passing through the waveguide. As used herein, the term doping may mean the injection or depletion of electrons and holes into a silicon optical waveguide. However, the performance of such devices has historically been limited by the fundamental trade-off between optical loss and increased resistivity, which may limit the operation speed through the resistor-capacitor (RC) circuit time delay (τ). In this type of optical modulator, the MOS capacitor may be placed close to the center of an optical waveguide, and the optical waveguide may be part of the electric path to the capacitor. To obtain a low series resistance and thus a high EO bandwidth, the waveguide may need to be doped at a relatively high level. However, the free carriers introduced by doping create optical loss in the waveguide, and consequently low doping may be desired to achieve low optical loss. Similar tradeoff also presents in the PN-junction-based EO modulators.